Merge pull request #5657 from leifurhauks/py3_generated_code

python 2/3 compatible abstract servicers/stubs

src/compiler/python_generator.cc

@@ -190,11 +190,10 @@ bool PrintBetaServicer(const ServiceDescriptor* service,
         "Documentation", doc,
       });
   out->Print("\n");
-  out->Print(dict, "class Beta$Service$Servicer(object):\n");
+  out->Print(dict, "class Beta$Service$Servicer(six.with_metaclass(abc.ABCMeta, object)):\n");
   {
     IndentScope raii_class_indent(out);
     out->Print(dict, "\"\"\"$Documentation$\"\"\"\n");
-    out->Print("__metaclass__ = abc.ABCMeta\n");
     for (int i = 0; i < service->method_count(); ++i) {
       auto meth = service->method(i);
       grpc::string arg_name = meth->client_streaming() ?
@@ -219,11 +218,10 @@ bool PrintBetaStub(const ServiceDescriptor* service,
         "Documentation", doc,
       });
   out->Print("\n");
-  out->Print(dict, "class Beta$Service$Stub(object):\n");
+  out->Print(dict, "class Beta$Service$Stub(six.with_metaclass(abc.ABCMeta, object)):\n");
   {
     IndentScope raii_class_indent(out);
     out->Print(dict, "\"\"\"$Documentation$\"\"\"\n");
-    out->Print("__metaclass__ = abc.ABCMeta\n");
     for (int i = 0; i < service->method_count(); ++i) {
       const MethodDescriptor* meth = service->method(i);
       grpc::string arg_name = meth->client_streaming() ?
@@ -449,6 +447,7 @@ bool PrintBetaStubFactory(const grpc::string& package_qualified_service_name,
 bool PrintPreamble(const FileDescriptor* file,
                    const GeneratorConfiguration& config, Printer* out) {
   out->Print("import abc\n");
+  out->Print("import six\n");
   out->Print("from $Package$ import implementations as beta_implementations\n",
              "Package", config.beta_package_root);
   out->Print("from grpc.framework.common import cardinality\n");